摘要:
Addition of 3 molar equiv of AlMe3 to (Me5C5)(2)Yb(ER)(NH3) gives two types of products depending on the identity of the ER group. When ER is OSiMe3 or TePh, the isolated metallocene is [(Me5C5)(2)Yb(Me4Al)](2), which exists as an equilibrium between monomeric and dimeric forms in toluene solution. When ER is OCMe3, SPh, S-p-tolyl, or SePh, the isolated metallocenes have the stoichiometry (Me5C5)(2)Yb(ER)(Me3Al)(2). The H-1 NMR spectra of these molecules show that several species are present in solution. The crystal structure of the S-p-tolyl derivative shows that two (Me5C5)(2)Yb fragments are bridged by two Me3Al(S-p-tolyl)AlMe3 units by way of nearly linear Yb...H3C-Al bonds.